In municipal landfills, one byproduct of the decomposition of solid waste is landfill gas, which predominantly consists of carbon dioxide and methane. These gases are recognized as “greenhouse gasses” known to be damaging to the environment and, therefore, the importance of effective landfill gas management has increased significantly over the past several years. This increase is due to: (i) tightened regulatory requirements for operations and reporting activities needed to comply with the Clean Air Act; and (ii) increased importance of efficient collection and processing of landfill gas that is used in waste-to-energy facilities. Given the current emphasis in society to develop sustainable and environmentally responsible processes, the need for improved landfill gas management will increase.
As is known, gas wells are used to capture the byproduct landfill gas in most landfill gas collection and control (i.e., management) systems. Typically, referring to FIG. 1, a landfill 100 has a number of wells distributed over an area that could cover tens, and possibly hundreds, of acres. Each well has a corresponding gas wellhead 102 that is an above-ground extension of the gas well. Operation of the gas wellhead 102, i.e., the flow of landfill gases, is controlled by adjusting a flow valve on the wellhead. In many cases, as is known, some of the gas wellheads are connected in series with one another while some are connected in parallel with one another. Experience has shown, however, that adjustments to one gas wellhead can influence the response of the other gas wells.
For proper operation of a landfill gas collection and control system, the gas flow rate, temperature and gas quality are measured at each wellhead 102 and the results of the measurements are compared to “expected values” that are based largely on experience. If the measured values for a single parameter are not within the expected range, then adjustments to the landfill gas flow are made by incrementally opening or closing the flow valve. It is well known, however, that when an adjustment is made at one gas wellhead, the flow (as well as other monitored parameters) at other wells may be impacted.
Ideally, a stable steady-state “tuned” condition is established at a landfill when acceptable performance is achieved and further adjustments to the control valve(s) are not necessary. However, it is well known that external factors, e.g., precipitation, temperature, and barometric pressure, as well as internal factors, e.g., cover soil thickness, waste age, thickness, composition and moisture content, change over time, constant measurements, assessments and adjustments at the gas wellheads need to be made.
Therefore, the “tuning” of the gas field to obtain consistent performance is a labor intensive activity, one that is exacerbated by the fact that, often, the tens (if not a few hundred) gas wells are adjusted by a lone technician who can probably make only one to two site visits per month.
What is needed, therefore, is a system to efficiently and accurately “optimize” the management of landfill gas.